This invention relates to the art of nailing machines.
Nailing machines normally comprise a main housing having a bore for holding a nail and a driving rod, slidable in the bore, for impinging on the head of the nail and driving it from the lower end of the bore into a board. In general operation, after a nail has been driven, a chuck bar on which the housing is mounted lifts the housing from the board while a driving head attached to the driving rod lifts the driving rod even further, so that it is partially pulled out of the bore of the housing. Once both the housing and the driving rod are in this lifted position, a new nail is fed into the bore from the side, and both the housing (under control of the chuck bar) and the head are moved downwardly until the housing is in contact with a board into which the new nail is to be driven. The driving head continues downwardly, urging the driving rod against the head of the new nail to drive the new nail from the housing into the board. The extent of movement of both the chuck bar and the driving head are preset in accordance with the thickness of the board into which nails are being driven. That is, the driving head moves downwardly in a driving stroke until it reaches a predetermined point, at which time both it and the housing move upwardly.
A problem with such prior-art nailing chucks is that it is often desirable to use them in making "rough" goods such as pallets from "rough-cut" lumber. The tolerances of such lumber are such that thickness dimensions vary upwardly to as much as three-eighths of an inch for pallets, for example. Most prior-art nailing chucks will not compensate for this 3/8" thickness differential and they must therefore be set to nail the thickest possible boards. This means that when the nailing chucks are used to nail thinner boards, the heads of the nails are left above the boards and must often be driven home by hand. Thus, when a battery of nailing chucks is usd to nail a pallet, for example, it is often necessary after each cycle for a workman to pound in nails that were not completely driven by the machine. It is therefore an object of this invention to provide a nailing chuck which compensates for uneven thicknesses of boards to drive all heads of nails into the boards, within a rather large range of board thicknesses.
An attempt was made to make a compensating nailing machine in 1926 by H. W. Morgan, as is disclosed in U.S. Pat. No. 1,605,053. However, the device disclosed by Morgan does not appear to be practical because it will probably not withstand the rigors of long operation as is required of nailing machines. In this respect, on every cycle of the Morgan machine, a shoulder 19 impinges heavily on a casting 10, thereby causing an undue pounding of both these members. Further, the operation of this machine relies on compression springs 21 and 28 which will not properly function over a large number of cycles. It is therefore an object of this invention to provide a compensating nailing chuck which is not unduly stressed on each cycle and which can continue to function accurately over a large number of cycles.
It is another object of this invention to provide a compensating nailing chuck which is relatively easy and inexpensive to manufacture.